Hydrocarbons, and in particular petroleum, are produced from the ground as a mixture. This mixture is converted to useful products through separation and processing of the streams in reactors and separation equipment. The conversion of the hydrocarbon streams to useful products is often through a catalytic process in a reactor. The catalysts can be solid or liquid, and can comprise catalytic materials. In bi-functional catalysis catalytic materials of acid such as zeolite and metals such as those in transition and main groups are combined to form a composite to facilitate the conversion process such as the one described in this subject application. During the processing of the hydrocarbons, the catalysts deactivate over time. One primary cause of deactivation is the generation and buildup of coke on the catalyst. The accumulation of coke covers or blocks access to catalytic sites on the catalyst. The regeneration of the catalyst is normally performed through the removal of the coke, where the coke is combusted at a high-temperature with a gas having oxygen. These processes can be performed either in a continuous manner with the catalyst cycled through the reactor and the regenerator, or the process can be performed in a semi-continuous manner, such as with multiple fixed beds, where one bed is taken off stream to regenerate the catalyst, while the other beds continue operation.
With the continuous regeneration process, a recycle gas is continuously passed to the combustion zone in the regenerator and a flue gas containing the combustion products is removed. The combustion process is controlled through the temperature and the oxygen content of the recycle gas. The recycle gas stream comprises a portion of the flue gas, and an additional stream of new combustion gas, while venting another portion of the flue gas from the regenerator. This helps maintain the temperature of the combustion gas, as well as setting up a steady state condition of continuous addition of spent catalyst and combustion gas to the regenerator, while continuously drawing regenerated catalyst and flue gas.
Catalyst regeneration methods are disclosed in U.S. Pat. No. 5,053,371 to Williamson, and U.S. Pat. No. 6,048,814 to Capelle, et al. for removing coke from catalyst particles through combustion. The combustion process can be damaging to the catalyst, and better methods of control of the combustion process are important for improving the life of the catalyst in the reactor-regenerator cycle. Frequency of regeneration for a given process is determined by the rate at which carbonaceous residue collects on the catalyst and causes conversion performance of the catalyst to decline. Processes that utilize molecular sieves also require continuous regeneration and have high susceptibility of chronic hydrothermal damage, significantly shortening catalyst stability, and overall life cycle. These types of processes need a regeneration design that minimizes the hydrothermal damage. Producing a better process allows for more cycles of the catalyst through the regenerator, and increases the life of the catalyst. This can be achieved through improvements in the process and control of the regenerator.
Coke deposits on the catalyst is made up of carbon and hydrogen where the combustion of hydrogen generates H2O as the combustion byproduct. Hydrocarbon processes such as dehycrocyclodimeraization utilize a catalyst made up of zeolitic material and hydrothermal de-alumination accounts for the majority of catalyst deactivation over the life of the commercial operation cycle. The propensity of zeolitic materials to dealuminate increases as water concentration and temperature increase. The standard design of catalyst regeneration burn zones are such that it can achieve complete coke burn and consequently due to high temperature requirements to achieve a regenerated catalyst carbon specification, burn zones operate at high severity.
Accordingly, it is desirable to develop methods for regenerating the catalyst that minimize the hydrothermal damage to the catalyst while maximizing coke burn. Furthermore, other desirable features and characteristics of the present embodiments will become apparent from the subsequent detailed description and the appended claims, taken in conjunction with the accompanying drawings and this background.